95 Chrysler Cirrus- Overheating, Limp mode

My chrysler cirrus has been overheating and i?ve had to add alot of coolant lately. The overheating is manageable as long as you are driving but once you come to a stop it becomes a problem. Yesterday on my way home from class I suddenly couldnt go past 2nd gear. From what I?ve read from other posts this seems to be "limp mode". When I drove it this morning, I could get into 3rd gear with no problems whatsoever until it began to overheat. So it seems that these 2 problems may be related. I discovered that the radiator fans were not kicking on so I replaced the coolant temperature sensor from my old pontiac just to see if that was the problem and sure enough they began to work. Thinking that this may have solved the entire problem, i was going to take it for a test drive but before I left my driveway the temperature gauge was maxed out already! I opened the hood and the engine was not hot at all! so i take it for a short drive and the transmission was working fine but the temp gauge would not go down so i quickly returned home. I have really dont know where to go from here...bad water pump? thermostat? simply a bad radiator cap???? Before I cluelessly bring it into the shop, i?d like to get some opinions. Thanks